Apparatus for ascertaining sighting and firing errors in gunnery practice



March 9, 1943. F. E. FISCHER 2,313,136

US FOR ASC INING SIGH G AND APPARAT ERTA FIRING ERRORS IN GUNNERY PRA CE F iled Nov. 26, 1938 3 Sheets-Sheet l INVENTOR! FRIEDRICH E. F'ITSGHER A TTORNEYS March 1943- I F. E. FISCHER 2,313,136

APPARATUS FOR ASCERTAINING SIGHTING AND FIRING ERRORS IN GUNNERY PRACTICE Filed Nov. 26, 1938 3 Sheets-Sheet 2 INVENTOR" Fmzszmzern E. F/5C'HER ,4414 A TTOIBNEKS.

March 9, 1943. F|$HER 2,313,136

APPARATUS FOR ASCERTAINING SIGHTING AND FIRING RRRoRs IN GUNNERY PRACTICE Filed NOV. 26, 19 3 3 Sheets-Sheet 3 I NVENTOR FIQ/EDR'ICH E F/SCHER I ATTORNEYS.

Patented Mar. 9, 1943 APPARATUS FOR ASCERTAINING SIGHTING AND FIRING ERRORS IN GUNNEBY PRAC- TICE Friedrich Ernst Fischer, Erlenbach, Switzerland Application November 26, 1938, Serial N6. 242,511 In Switzerland January 14, 193':

15 Claims.

The present invention relates to improvements in devices and apparatus for ascertaining sight- .ing and firing errors in gunnery practice against moving targets, especially in anti-aircrait gunnery practice; and the objects oi the improvements are, first. to provide an apparatus which will simplify and speed up the procedure of observation and computation involved in such target practice; and, second, one which will determine directly the sighting and tiring errors with the aid of a delaying device which artificially increases the time of transmission oicertain data characterizing a translatory movement or adjustment so as to take into account certain variables determining the accuracy oi sighting and tiring.

This application is a continuation-in-part of my application, Ser. No. 138,015, filed March 25, 1937.

The causes oi sighting and firing errors are well known. They originate in the iact that, when a moving object is tired at, it is necessary, owing chiefly to the time oi fiight oi the projectile, to aim the gun at a point which the target has not yet reached at the moment when the gun is aimed. In order to determine this point, it must be assumed that the target will follow a trajectory to which, however, it need not necessarily adhere. A sighting or firing error arises whenever this hypothetical trajectory does not coincide with the actual trajectory iollowed by the moving target.

The ascertaining oi sighting errors in antiaircrait gunnery practice has heretofore been accomplished almost exclusively by means oi photogrammetric surveys and subsequent lengthy comutations, .and has accordingly proved complicated and tiresome. In accordance with the present invention, the directional readings oi two transits or theodolites, as well as those oi the gun and the timing apparatus ior the gun, are transmitted continuously to a central apparatus by way oi remote control, and the time required for the transmittance oi the said readings or settings oi gun and timing apparatus is artiricially increased-in a fixed or variable measure-by means oi special delaying devices. Any other kind of sighting device-known per se-- may take the place oi the said theodolitesior the purpose at surveying or intersecting the true position oi the airplane. The theodolites or the sighting devices also may be connected with photographic camera shutter mechanisms ior verincatlon purposes or ior the purpose oi simultaneously ascertaining both sighting and firing errors.

The accompanying drawings show schematically by way of example, an arrangement embodying the present invention. In said drawings,

Fig. i; and

Fig. 3 shows in detail the construction oi the coordinate changing and computing mechanism.

Fig. 4 is a diagrammatic view illustrating one spatial arrangement or the sighting devices or theodolites and the object sighted, and indicating also certain of the measured and computed variables, the theodolites being at different elevations.

The apparatus according to the invention for the measurement oi gunnery errors consists essentially in the combination oi a central apparatus 4 which contains a computing mechanism ior determining the distance between two points, with a delay mechanism 8 which registers the movements oi an electrical sender and transmits such movements aiter an adjustable delay interval. As will be explained more fully below, the central apparatus is so connected with a gun and its ignition mechanism as well as with two sighting devices by means oi electrical conductors that both the positions oi the gun and its timing mechanism as well as the positions oi the two sighting devices or theodolites are transmitted continously by remote control to the central apparatus. The theodolites sight the moving target continuously, while the gun is aimed repeatedly at a "be" or iuture position of the target: hence, in order that the computing mechanism may compare the iuture position of the target, as fixed in space by the gun adjustments, with the actual position oi the target at the iuture moment as determined by the two theodolites, in order to compute the sighting error, it is necessary that the time ior the transmission oi the values oi the movements oi the gun and the timing mechanism to the central apparatus be delayed by the time required ior the projectile to reach the assumed iuture position 01' the target (also called "point oi aim). This is accomplished in accordance with the invention by the cutting in of a delay-producing Jnechsnism into the electrical conductors between the gun and the timing race on the one hand, and the central apparatus on the other. Accordingly, the transmission time for the gun data is artificially increased by a fixed or variable extent depending upon the time of flight of the projectile.

In the practice of my invention, the moving target I, i. e. an airplane, is followed up and intersected by means of sighting devices, e. g. by means of two transits or theodolites 2 and 3. Let the co-ordinates, i. e., the elevation and azimuth readings, measured by the two transits be in and vi and u: and 172, respectively, the base line for the directional or azimuth readings being the horizontal line b' (Fig. 4) connecting the theodolites 2 and 3, or their projections on a horizontal plane. The true position of the airplane is thus given by the readings of the two transits. The said settings are transmitted to the central apparatus 4 by way 01' electric remote control. The two transits or theodolites] and 3 are directed continuously at the progresively changing positions of the target. and the co-ordinates in, D1, and ill, or of the two theodolites are continuously transmitted to the central apparatus 4. As the two theodolites are at considerable distances from each other (as much as several kilometers), the central apparatus includes a coordinate changer which reduces the co-ordinates of the two theodolites to the same co-ordinate system, i. e. to measurements with reference to the same base line and zero point and thereby the progressive actual positions 01' the airplane in space are determined in the central apparatus 4.

The gun 5 is, or course, set toward a point in front of the moving airplane considered in the direction of movement 01' the latter. The distance and direction oi this point of aim (tuture position) from the position oi the airplane at the moment of flring are determined in known manner from the assumed time of flight or the projectile, the speed oi the airplane, and the sighting data. The settings of gun and timing apparatus 5 similarly are transmitted to the central apparatus 4 by way of electric remote control.

The assumed time 01' flight of the projectile being T, the function 01' the central apparatus 4 is to determine the relative positions of the projectile and the airplane after this'time T has elapsed. To this end, the central apparatus is provided with coordinate changing and computing mechanism which may be of the type shown main delayer 8 by way of the lines 8-H, and there delayed for the amount of time anticipated for the shell to cover its trajectory; this length of time, which also is called time of flight, corin my Patent No. 2,283,922, dated May 28, 1942,

serial No. 242,510, flled simultaneously herewith, or or any other suitable construction. The actual osition 01 the arplane is determined by the coordinates ot the theodolites 2 and l: the theoretical position of the projectile. on the other hand,

is determined by the coordinates of the gun 8. However, since the coordinates oi the gun change more or less continuously, and even immediately after the flring oi the projectile, it is necessary to introduce into the central apparatus 4 simultaneously with the coordinates oi the theodolites 2 and 3 at the end of the time of, flight T, the coordinates oi. the gun It at the moment that the flight began Transmission oi. the coordinates oi. the gun 5 and timing mechanism to the central apparatus 4 must accordingly artiflcially be delayed by the assumed time oi flight o! the projectile, which may be flxed or variable. This is the function 01 the delaying apparatus 0 and I. The transmitting lines 8l4 serve {or translating the gun or ballistic coordinates or data, such as side or azimuth S. elevation E and timing T. from the gun It to the central apparatus 4.

responds to the timing T. After the said time of delay has elapsed, the said data S, E and T are dispatched to the central apparatus by way of the lines l2--l4.

The assumed time of flight of the projectile, according to which the gun has been set, is likewise transmitted to the central apparatus 4. This time of flight begins. of course, with the flring of the gun. and as an appreciable interval elapses between the setting of the timer and the actual flrin'g oi the gun, the transmission or this timing value may be and preferably is further delayed in a pre-delayer l by a period, called the charging delay, which corresponds to the interval between the moment oi setting of the timing or the primer and the moment of flring.- The pre-delayer I is interposed in the transmitting line Ill-ll (which serves for transmitting the timing value T) between the gun or the appurtenant timing apparatus 5 and the main delayer 8.

The thus pro-delayed timing value T, together with the data 8 and E of the gun at the moment of flring. form the simultaneously appurtenant valuesoi the gun or ballistic coordinates oi the future target position or point of aim.

The line I! not only transmits the timing value T onto the main delayer 8 for the purpose of delaying the further transmittance, but at the same time controls the delay by regulating the latter automatically by remote control or by means of a follow-up indicator adjusted by hand in accordance with the timing T (time of flight). The delaying mechanism, the preferred form of which is described hereinbelow, is in general known: see, for example, United States Patents Nos. 1,891,652, 1,809,070, 1,883,907; 1,979,998, and 2,079,959: German Patents Nos. 216,938, 425,109 and 668,994: and British Patent No. 348,154.

The flring signal A may be transmitted onto the transits 2 and I by the lines l8 and I1; the flring signal A-in the case 01. photo-theodolites-may be made to operate the shutter mechanisms at a moment delayed by the time or flight of the projectile.

The central apparatus 4 thus receives simultaneously the coordinates of the theodolites 2 and 3 corresponding to a given moment, and the coordinates of the gun and the assumed time oi flight-corresponding to an earlier moment. In such central apparatus 4 the sighting error is continuously determined fromthe coordinates of the true position of the airplane and those of the theoretical point oi bursting as the distance between the said two points. The sighting error may" be registered in. or read from an instrument The individual mechanisms forming part or my improved arrangement maybe built in any known manner. Thus the computing mechanism for measuring the distance between two points, the coordinate changers and the delay-producing devices may follow known constructions and principles. The delaying mechanism may, for example. be or the continuous belt type and may be constructed in the manner illustrated in my Patent No. 2,162,707, dated June 20, 1939 and in my application Serial No. 242,510, above referred to.

However. in order that my invention may be The latter data 8, E and 'r are sent to the is better understood, 1 have illustrated in Figs. 2

and 3 the detailed construction of certain of the devices shown schematically in Fig. 1.

Fig. 2 shows by way of example one form of construction of a delaying device with three transmission channels.

in the diagram, It represents an electric control unit, which converts a rotary movement rcpresented by the hand-wheel 20 on its shaft it) into electrical impulses by connecting either one or two of the three circuits 22, 23 and 24 together with the c mmon return channel 2! and the battery 26 )y which means the direction and degree of movement are definitely characterized in a manner known in itself. Circuits 21, 21 and 24 each include a so-called s eaker head 21, 2| and 2!, respectively, consisting of a coil which, when current is passed through it, magnetises at corresponding places n steel tape which is conducted past it. The steel tapes 8|, SI and I! are conducted over rollers. 11, N and it respectively, which are mounted three to a shaft. One of these shafts is rotated, in a manner not shown in detail, at a constant number of revolutions per minute. the direction of rotation being indicated in Fig. 2 by means of an arrow.

The electrical impulses characterising the movement and transmitted by the speaker heads 27, ft and 2! in the form of magnetic registrations on the steel tapes III, II and II. are retransformed into electrical impulses in the hearer heads It, 31 and it. A hearer head consists essentially of a coil in which an electric current is induced when a magnetised portion of the steel tape is led past it. The currents induced in the hearer heads It, 31 and 3! are amplified and conducted via the channels ll. 4' and II to relays l1, 4! and 44, and in their passage close the corresponding circuits 4|, 4| and/or 41 together with the battery I in the common return channel 4!.

The electrical impulses flowing in these latter circuits thus correspond exactly with those in circuits 22 to It, thus also characterising the movement to be translated in the shaft 2|. They are conducted in known manner to the stator coils 50, BI and 52 of a receiver motor, the rotor 51 of which adjusts itself according to the current passing through and the shaft ll of which accordingly executes the same movement as shaft 2|. The position of the control II at any time can therefore be read of! on an indicator It.

The movement of shaft ll thus corresponds exactly to the movement of shaft 2|, there only intervening between the two a certain interval (time of run) which is identical with the period elapsing between the magnetic registrations in the sending devices 21. ii and 2!, and the reception of these registrations and their re-conversion into electrical impulses by the bearer heads ll, 81 and ll. This so-called running time of the translation of the movement can be altered in a simple manner, e. g. by displacing similarly the bearer heads I, 81 and Il along spindles ll, 51 and it by means of a hand-wheel ll. 'In order to render the steel tapes receptive for new registrations after previous registrations have been transferred to the bearer heads I, 81 and a, so-called erasing coils "a are provided in known manner.

Fig. 8 shows a detailed diagram of one form of construction of the central apparatus 4 together with the appurtenant co-ordinatc converters and computing apparatus,

The settings, 1. e. the ballistic co-ordinates of side or azimuth B, elevation E and timing T emanating from the gun I are transferred, after being each retarded by the assumed time of flight of the projectile in the delaying device 8, by means of the shafts ll, 05 and 68 to the ballistic co-ordinate converter N, which consists essentially of the three cams 60, ti and 82. This type of mechanism is known and is shown in greater detail in German Patents Nos. 620,385 and 611,497. The timing T is not, however, taken of! the gun simultaneously with the vales B, E and the firing signal A, but rather earlier by the time which is necessary for the charging of the gun. The transmission of the timing value must, therefore, be delayed additionally by this so-called charging period, and this occurs in the pre-delayer mechanism 7.

Cam ll, for example. is out according to the lateral deviation (lateral divergence of a projectile path from the vertical plane established by the axis of the gun-barrel) so that the value taken of! cash I as a function of elevation E and timing '1 can be added in the differential 81 to the ballistic side 8 (shaft I4) and thus yields the azimuth As at the shaft 88. The latter is suitably oriented upon the base direction (line connecting theodolites 2 and I) as the zero direction.

The two cams Ii and I! are similarly cut in dependence upon elevation and timing corresponding to the horizontal projection of the target distance D and to the target height as, referred to the gun. The obtained values of azimuth and horizontal projection of the target distance are transmitted to the sine-cosine drive a, in which the horizontal projection of the target distance is resolved into its components in relation to a horizontal rectangular :c, y-co-ordinate system. The sine-cosine mechanism is likewise known and may be of the type shown in German Patents Nos. 870,956, 578,764, 607,318 and 847,296.

To enable comparison to be made of the coordinates of the airplane position I (m and Ul, us and vs respectively) measured by the two theodolites 2 and 3, with the ballistic co-ordinates convertedinto :co, m and 20, they must likewise be converted into co-ordinates of the v. I co-ordinate system.

When the theodolites are set by the co-ordinates u (azimuth) and 9 (angle of ground=angle of sighting direction to horizontal plane), this conversion can be accomplished mechanically, for example, according to the known mathematical relationships:

sin u .sin u: a who) sinu,

In these equations. 1) indiciates the horizontal projection of the'base length, i. e. the horizontal distance between the two theodolites 2 and I. The co-ordinates :1, vi and :1 are illustrated in Fig. 4 and are referred to the position of theodolite I as the co-ordinate zero point and the base direction as the direction of the :c-co-ordinate. The magnitude sin 14,

sin 214 +111) is taken of! cam "a in the form of construction and sin 11:

ill

are obtained,

The value of 21 is obtained at the shaft 12 by multiplication of the term sin u, m

by tg or with the aid of the corresponding y out cam 13. In the form of construction illustrated, the value of Zl is determined quite analogously according to the formula sin u.

sin (u -i-m) Ah representing the difference in height of the theodolites 2 and 3, for which allowance can be made by means of the hand-wheel H by way of the differential IS. The mechanism for evaluating the above formulas is known,,and may be of the type illustrated in German Patents Nos. 370,956, 433,936, 567,054 and 632,489.

A double tracing (double determination) of 21 is necessary in order to avoid the singularity position of the selected u, v co-ordinate system which occurs when the airplane I flies vertically over the base point which was selected as the coordinate zero point. To this end the cams l8 and 11, as well as the multiplication drive II and the differential 18, are required, these parts yielding the second value of Z1 at the shaft 18. By means of the couplings 88 and 8|, one of which is always thrown in when the other is thrown out, one or the other value of in can be selectively transmitted to the shaft 88 through the bevel wheels 82. The reversal of the couplings 88 and 8| is effected by closing an electrical circuit. Such .a circuit is. for example. closed by the pairs of contacts 88 and '88 when the value b sin u,

sin zu -i-u b sin u 'si Z i 4) falls below a definite value.

The electric circuit which disconnects the windings in parallel circuit.

for constructional reasons and further would lead to uncertainty in the measurement.

The values :m, m and Z1 obtained in this way at the shafts 18, II and 83 suilice to fix definitely the position of the aircraft in space. They are, however, referred to the position of the theodolite 2 as the co-ordinate zero point; in order that they may be compared directly with the converted ballistic co-ordinates mu, 1/0 and 20 referred to the gun position, parallax corrections be applied to them. This is accomplished in simple and known manner by the addition of the parallax corrections to the co-ordinates :m, m and z: of the aircraft's position by means of the diflerentlals 88, 81 and 88.

The ascertaining of the distance between two points (position 01 aircraft and theoretical bursting point of the projectile) which are given in the same co-ordinate system (1, fl. 2) is effected in known manner with simple computing apparatus. In the example of construction illustrated in Fig. 3 the components of the distance are first determined, these,as is known, being (so-s1). (yo-m) and (av-21'), and are formed in the differentials 84, 88 and 98: Z, the distance proper, i. e. the aiming error, is then yielded by the relation:

Corresponding to the values of the components (to-31'); (lie-111') and (Zn-21) obtained at the shafts 81, 88 and 88, the withdrawn secondary voltages are regulated at the three electric transformers I88, IOI and I02 with primary If the secondary windings of the transformers I08, I81 and I82 are so constructed that the withdrawn voltage increases quadratically with the displacement of the current remover I88, I04 and I05, the sum of the partial voltages withdrawn atthe three secondary windings corresponds to the square of I the sighting error. and the sighting error itself coupling 80 or 8| is indicated schematically in Fig. 3 by the electrical connection to shatter! and the two contacts 88 and 88. The coupling is of the electromagnetic type. that is. it becomes engaged when an electric circuit is closed. The closing of the circuitis accomplished for 'example by small switches which are actuated can be read oi! at-an instrument I8 provided with suitable scale graduation. A construction of this type is illustrated in German Patent No. 370,956 above referred to.

I claim:

'1. An apparatus according to claim 14 wherein the delay mechanism includes an electromagnetic circuit with at least one sender and one receiver, and at least onetravelling endless steel tape for receiving magnetic registrations of the movements-of the said sender for the purpose of delaying the transfer of the said movements to the said receiver.

2. An apparatus according to claim 14, wherein the delay mechanism includes an electromagnetic circuit with at least one sender and one receiver, and at least one travelling endless steel ratus is adjusted according to the individual time of flight of the projectile.

4. An apparatus according to claim 14 including means for effecting the said artificial increase of the time of transmission in a plurality of steps.

5. An apparatus according to claim 14, wherein the sighting devices comprise two theodolites.

6. An apparatus according to claim 14, wherein the said artificial increase of the transmission time takes place ahead of the transformaiion oi co-ordinates.

7. An apparatus according to claim 14, wherein the said artificial increase the transmission time takes place between the transformation 0! co-ordlnates.

8. An apparatus according to claim 14, wherein the said artificial increase oi the transmission time takes place after the transformation of coordinates.

9. An apparatus according to claim 14, including a travelling endless steel tape operating as a pre-delayer: the said tape taking into account the so-called charging delay and correspondingly pre-delaying the transier oi the timing ior an adjustable length oi time in order to enable one to obtain simultaneously appurtenant values of the ballistic co-ordinates, side, elevation and timing.

10. An apparatus according to claim 14, including a steel tape, speaker-heads and hearerheads, and characterized in that the length oi the said tape between the said two classes of heads is variable ior the purpose of increasing the time oi run 01 a translatory movement.

11. Apparatus for determining sighting errors in gunnery practice comprising, in combination. a sighting mechanism adapted to be directed continuously at a moving target. a central apparatus, means connecting the latter with said sighting mechanism and acting to transmit thereto the coordinates oi such mechanism, said central apparatus including computing mechanism operative to determine the position or the target from such coordinates, means for transmitting to said central apparatus the settings or a gun and its timing mechanism, and mechanism for delaying the transmission to said computing mechanism of the settings of the gun and timing mechanism, and means in said central apparatus for relating the position of the target with the point of aim as established by the settings or the gun and thereby determining the sighting error.

12. Apparatus according to claim 11, wherein the delaying mechanism comprises a uniformly moving magnetizable member, a speaker head adapted to convert electrical impulses corresponding to the settings of the gun and timing mechanism into magnetic registrations on said member and a hearer head associated with said member in spaced relation to said speaker head and acting to convert said magnetic registrations into electrical impulses, said hearer head being connected with said central apparatus.

13. Apparatus according to claim 11, including a predelayer for additionally delaying the transmission of the setting oi the timing mechanism by the time interval elapsing between the moment oi setting such mechanism and the instant of firing.

14. Apparatus for surveying and registering sighting errors in shooting practice against moving targets, such as airships, comprising the combination of a central apparatus including a computing device for determining the distance between two points, an electrical sender for converting the adjustments at a gun station into electrical impulses. a delay-producing mechanism for registering the movements of the electrical sender and transmitting the impulses after a predetermined period oi delay. two Sighting devices, and electrical conductors between the central apparatus on the one hand and the gun and its timing mechanism and the two sighting devices on the other, said conductors transmitting both the settings or the gun and timing mechanism as well as the settings oi the two sighting devices continuously to the central apparatus, said delay mechanism being interposed in the conductors between the central apparatus and the gun and its timing mechanism, whereby the duration of the transmission or the movement oi! the gun and timing mechanism to the central apparatus is brought into relationship .with the time oi flight oi the projectile at any time by the said delay mechanism by beingartiflcially increased in correspondence with such time o! flight by the said predetermined period of delay.

15. An apparatus according to claim 14. including photographic cameras for verification and recording. each of said sighting devices being provided with a photographic camera, the openin or the shutter mechanisms or the said cameras being controlled by the nring signal at a moment delayed by the time oi night of the projectile.

FRIEDRICH ERNST FISCHER. 

